Emacs-for-Goodness-Sake

Chapter 11: Macros and Registers

Automation for Humans (And Cyborgs)

Imagine if you could record yourself editing text, then replay that recording 1000 times. Now imagine if you could save snippets of text or positions in variables you can instantly recall. That’s macros and registers. Together, they turn repetitive tasks into a single keystroke and make you look like you’re hacking the Matrix when really you’re just editing a CSV file.

This is where Emacs stops being a text editor and starts being a text manipulation engine that responds to your will.

Keyboard Macros: Your Personal Robot

The simplest way to record a macro:

F3     - Start recording
...    - Do stuff
F4     - Stop recording
F4     - Play it back

That’s it. You just automated something.

🚸 IDE Refugee Note: This is like recording actions in Photoshop or Excel, except it works everywhere in Emacs, on any text, in any mode. And it’s been here since the 1970s.

A Real Example

Let’s say you have:

alice
bob
charlie
dave

And want:

User: alice (ID: 1)
User: bob (ID: 2)
User: charlie (ID: 3)
User: dave (ID: 4)

Here’s how:

1. Position cursor at start of “alice”
2. F3 - Start recording
3. C-a - Beginning of line
4. Type: User:
5. C-e - End of line
6. Type: ` (ID: 1)`
7. C-n - Next line
8. F4 - Stop recording

Now the magic:

• F4 - Applies to bob (but with ID: 1)
• C-u 2 F4 - Applies to next 2 lines

But wait, the ID doesn’t increment! Let’s fix that…

The Macro Counter

Emacs has a built-in counter for macros:

1. F3 - Start recording
2. C-a - Beginning of line
3. Type: User:
4. C-e - End of line
5. Type: ` (ID: `
6. C-x C-k C-i - Insert counter (starts at 0)
7. Type: )
8. C-n - Next line
9. F4 - Stop recording

Set the counter before running:

C-x C-k C-c 1 RET    ; Set counter to 1
C-u 3 F4             ; Apply to next 3 lines

Now each line gets an incrementing ID!

Macro Ring: Multiple Macros

You can have multiple macros:

• C-x C-k C-k - Execute second-to-last macro
• C-x C-k C-n - Cycle to next macro in ring
• C-x C-k C-p - Cycle to previous macro

Editing Macros: Yes, You Can Debug Them

Made a mistake? Edit the macro:

C-x C-k C-e    ; Edit last macro

This opens a buffer showing your macro as text:

C-a            ; beginning-of-line
User: SPC      ; self-insert-command * 6
C-e            ; end-of-line
...

Edit it like any text, then C-c C-c to save.

Saving Macros Forever

Turn your macro into a function:

C-x C-k n my-awesome-macro RET   ; Name it
M-x insert-kbd-macro RET          ; Insert as Elisp

This generates:

(fset 'my-awesome-macro
   "\C-aUser: \C-e")

Put this in your config and bind it:

(global-set-key (kbd "C-c m") 'my-awesome-macro)

Advanced Macro Techniques

Conditional Macros

Use search to make macros conditional:

1. Start macro
2. C-s pattern - Search for pattern
3. If found, do something
4. End macro

If search fails, macro stops. Perfect for processing only certain lines.

Recursive Macros

A macro that calls itself:

1. Record macro that does something and moves forward
2. At the end, add F4 (call-last-kbd-macro)
3. Stop recording
4. Run once - it runs forever (until error)

Query in Macros

C-x q    ; Query user during macro

When macro runs, it pauses and asks for confirmation.

Registers: Your Multi-Clipboard

Registers are single-character variables that can store:

• Text
• Numbers
• Positions
• Window configurations
• Rectangles
• Macros

Text Registers

C-x r s a    ; Save region to register 'a'
C-x r i a    ; Insert contents of register 'a'

Example workflow:

1. Select boilerplate text
2. C-x r s b - Save to register ‘b’
3. Later: C-x r i b - Insert boilerplate

Position Registers

C-x r SPC a    ; Save position to register 'a'
C-x r j a      ; Jump to position in register 'a'

Perfect for jumping between locations:

1. C-x r SPC h - Mark header location
2. C-x r SPC f - Mark footer location
3. Edit in the middle
4. C-x r j h - Jump back to header
5. C-x r j f - Jump to footer

Number Registers

C-u 100 C-x r n a    ; Store 100 in register 'a'
C-x r i a            ; Insert 100
C-x r + a            ; Increment register 'a'

Use case: Counters in macros:

(defun my-numbered-list ()
  "Insert a numbered list item."
  (interactive)
  (insert (format "%d. " (get-register ?n)))
  (set-register ?n (1+ (get-register ?n))))

Window Configuration Registers

C-x r w a    ; Save window configuration to 'a'
C-x r j a    ; Restore window configuration

This saves your entire window layout:

1. Set up complex window arrangement
2. C-x r w z - Save to register ‘z’
3. Work in single window
4. C-x r j z - Restore layout instantly

Rectangle Registers

C-x r r a    ; Save rectangle to register 'a'
C-x r i a    ; Insert rectangle

Combined with rectangle commands, this is powerful for column editing.

Combining Macros and Registers

This is where the magic happens:

;; Macro that uses registers
F3                    ; Start macro
C-x r i h            ; Insert header from register
C-n                  ; Next line
... do stuff ...
C-x r i f            ; Insert footer from register
F4                    ; End macro

Practical Examples

Converting CSV to SQL

Starting with:

John,Doe,30
Jane,Smith,25
Bob,Johnson,35

Want:

INSERT INTO users (first, last, age) VALUES ('John', 'Doe', 30);
INSERT INTO users (first, last, age) VALUES ('Jane', 'Smith', 25);
INSERT INTO users (first, last, age) VALUES ('Bob', 'Johnson', 35);

Macro:

1. F3 - Start
2. C-a - Beginning of line
3. Type: INSERT INTO users (first, last, age) VALUES ('
4. C-s , - Search for comma
5. Type: ', '
6. C-s , - Next comma
7. Type: ',
8. C-e - End of line
9. Type: );
10. C-n - Next line
11. F4 - Stop

Creating Test Data

Generate 100 test users:

(defun generate-test-users (n)
  "Generate N test users."
  (interactive "nNumber of users: ")
  (dotimes (i n)
    (insert (format "User_%03d,user%03d@example.com,password%03d\n" 
                    i i i))))

Or with a macro using the counter:

1. C-x C-k C-c 1 - Set counter to 1
2. F3 - Start macro
3. Type: User_
4. C-x C-k C-i - Insert counter (formatted with leading zeros)
5. Type: ,user
6. C-x C-k C-i - Insert counter again
7. Type: @example.com
8. RET - Newline
9. F4 - Stop
10. C-u 99 F4 - Create 99 more

Advanced Register Usage

Register List

View all registers:

C-x r l    ; List registers

Append to Registers

C-x r + a    ; Append to text register
C-u C-x r s a ; Prepend region to register (with prefix arg)

Register Persistence

Save registers across sessions:

(savehist-mode 1)
(add-to-list 'savehist-additional-variables 'register-alist)

Bookmarks: Named Position Registers

Bookmarks are like permanent, named position registers:

C-x r m      ; Set bookmark
C-x r b      ; Jump to bookmark
C-x r l      ; List bookmarks

They’re saved automatically and persist across sessions.

Real-World Macro Workflows

The Refactorer

Convert function calls from oldFunc(a, b, c) to newFunc(c, b, a):

1. F3 - Start macro
2. C-s oldFunc( - Find function
3. C-f - Enter parens
4. C-M-f - Move forward over first argument
5. Mark argument and C-x r s 1 - Save to register 1
6. C-d - Delete comma
7. Continue for other args…
8. Reassemble in new order
9. F4 - Stop

The Data Transformer

Transform JSON to YAML:

(defun json-to-yaml-macro ()
  "Macro to convert JSON to YAML."
  (interactive)
  (kmacro-set-counter 0)
  (while (re-search-forward "\"\\([^\"]+\\)\": " nil t)
    (replace-match "\\1: ")
    (when (looking-at "\"\\([^\"]+\\)\"")
      (replace-match "\\1"))))

Macro Best Practices

1. Start simple: Record basic macro first, enhance later
2. Use searches: Make macros resilient to line variations
3. Test on one: Before applying to 1000 lines
4. Save good ones: Name and bind frequently used macros
5. Combine with registers: For complex transformations

Debugging Macros

;; Step through macro execution
(setq kmacro-step-edit-mini-window-height 15)
C-x C-k SPC    ; Step-edit macro

;; See what macro does
C-x C-k C-v    ; View last macro

;; Ring management
C-x C-k C-d    ; Delete head of macro ring

🎮 Macro and Register Exercises

1. The Formatter: Record a macro that formats messy code
2. The Generator: Create test data with incrementing IDs
3. The Transformer: Convert between data formats (JSON→CSV)
4. The Navigator: Set up position registers for a large file
5. The Automator: Create a complex macro using multiple registers

What’s Next?

The Appendix awaits with a survival guide for IDE refugees—tips and tricks to make your transition from VS Code/IntelliJ/Sublime as smooth as possible.

But now that you know macros and registers, you’ve unlocked Emacs’s automation superpowers. You can record any sequence of actions and replay it endlessly. You can store and recall text, positions, and window configurations instantly. You’re not just editing text—you’re programming your editing.

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“I spent 2 hours writing a macro to save 5 minutes of work. Totally worth it because I’ll use it again. Maybe. Probably. Okay, it was just fun.” —Every Emacs User Eventually

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Chapter 11 Summary

• Macros record keystrokes, replay them infinitely
• F3/F4 is your quick record/play
• Counters make macros dynamic
• Registers store text, positions, numbers, configurations
• Single character variables at your fingertips
• Combine macros and registers for complex automation
• Save macros as functions
• Debug and edit macros like code
• You’re now an automation wizard 🧙‍♂️

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